During Phase I of our research project, we developed a microarray system that can be used to measure the expression of known miRNAs in human, mouse, or rat samples. We used the microarray system to analyze tumor and normal adjacent tissues from patients with lung, colon, breast, prostate, bladder, thyroid, and pancreas cancer. Each tumor type could be readily distinguished from the accompanying normal samples based on the expression levels of 3-10 miRNAs. While each different tumor type was characterized by its own unique miRNA profile, it is interesting to note that several miRNAs appear to be up- or down-regulated in almost all tumor samples relative to normal adjacent tissue samples. This suggests that specific miRNAs might play roles in tumor suppression. Putative mRNA targets for a number of these miRNAs are known oncogenes providing a potential link with oncogenesis. We have verified that the expression of two well- known oncogenes is regulated by one of the miRNAs that was found to be differentially expressed in cancer samples, providing a potential link between reduced miRNA expression and oncogenesis. During Phase II of our research project, we will create methods for, isolating, amplifying, and labeling the miRNA in a sample to enable the analysis of small samples like those that result from needle biopsies and laser capture microdissection (LCM). The amplification method will facilitate studies of miRNA expression in specific types of cancer cells within the tumors of cancer patients and allow researchers to better understand how miRNAs contribute to oncogenesis. We will use the procedure that we develop to analyze LCM samples from lung and colon cancer tumors and normal adjacent tissues to verify that miRNA expression does differ between cell types in tissues. [unreadable] [unreadable] [unreadable]